dozimetr1Narrated by Anatoly Ivanishin

It is a known fact that (Earth – ed.) atmosphere protects us (humankind – ed.) against (space – ed.) radiation. So what are we (cosmonauts – ed.) to do in space at an altitude above 100 km? The level of radiation hazard is significantly higher here. However, it is possible to live in space. Besides atmosphere, our protection from radiation also comes from the Earth magnetic field. Tej first Earth radiation belt is at the altitude of about 600-700 km. The station is now flying at the altitude of about 400 km, which is significantly lower than the altitude of the first radiation belt. Protection against radiation in space is (also – ed.) provided by the spacecraft or station hull. The thicker the walls, the greater the protection. Of course, the walls cannot be infinitely thick because of the mass constraints. We cannot put into orbit payloads (spacecraft and stations – ed.) with very thick walls. However, besides the walls we can rely on our knowledge about the nature of radiation.

Since 2004, Matryoshka experiment has been conducted onboard ISS. Obtained in the course of this experiment were the data that the radiation level decreases several times over as you move away from the hull. Right now I’m at the center of the large diameter of the Service Module working compartment. Radiation level is probably lower here (according to dosimeter readings it was several times lower – ed.).

Throughout the entire mission cosmonauts are supposed to wear personal dose meters which look like this one. During the mission this meter accumulates (measures – ed.) the radiation, to which we are exposed, and upon our return to Earth specialist determine the dosage. There is such a notion as total maximum dose (total professional dosage limit for a cosmonaut – ed.) Over a mission lasting half a year the value of the total maximum dose is about one tenth of the dose a cosmonaut can get over his entire career (that is, during a mission lasting about half a year a cosmonaut receives about one-tenth of the dose limit per a cosmonaut – ed.).

Background level of ionizing radiation on the international space station is higher than on Earth (approximately by a factor of 200 – Ed.), which makes cosmonauts more exposed to ionizing radiation than workers in traditionally radiation-hazardous occupations such as nuclear power generation and X-ray diagnostics.

In addition to personal dose meters, cosmonauts onboard the station also have a radiation monitoring system. The system consists of a power and switching unit, pulse analyzer unit and 4 dose meter sensors. All components of the system are located in the Service Module. One sensor is located in each of the crew quarters, one sensor is in the small and one in the large diameter of the working compartment. The system operates autonomously 24 hours a day. Data from the sensors, and each sensor has two independent measuring channels, go to the power and switching unit, and from there to the pulse analyzer unit. The pulse analyzer unit forms telemetry frames, which are subsequently buffered and via the system BITS2-12 (onboard telemetry data system) the data are downlinked to the mission control in Moscow. Thus the ground has the data on the current radiation environment onboard the station. The radiation monitoring system is capable of issuing a warning signal "Check Radiation!". If this had happened, we would have seen a light lighting up on the systems caution and warning panel accompanied by a sound. There have never been any such incident onboard the International Space Station over its entire life.

Development of personal means of protection against radiation continues all the time. I would like to tell you about one of the recent developments in this field. It is called "protective screen”. It is installed in the crew cabin. The screen was delivered to the International Space Station in July 2010. In practice, the screen is an assembly, installed inside which are some tissues. These are wet tissues used by the crew as personal hygiene items. The packing and the soak are made of materials containing carbon, hydrogen and nitrogen which effectively reduce space radiation. By the way, that’s how the tissue looks like.

In the opinion of Russian scientists, installation of such a screen is capable of reducing negative effects of radiation on crew health. A preliminary analysis of data obtained in the course of experiments suggests that the screen absorbs radiation with about 40% efficiency. The maximum absorbtion is achieved in the center of the screen and falls off towards its edges.

Narrated by Anton Shkaplerov

We continue to describe to you the methods of studying radiation dosages, which a cosmonaut receives during a mission. Currently, expeditions stay onboard the station for as long as half a year. Scientist are interested in learning which organs are exposed to radiation and how much of it they take during a mission. We have already mentioned that cosmonauts over the period of their mission receive up to 0.1 of the total professional dose limit. 

Many years of studies conducted with the use of Matryoshka-R experiment have shown that different organs receive different radiation doses during a mission. It depends on how deep is the organ. That is, the radiation decreases as you go from a human being’s skin surface to his or her deeper internal organs. 

Experimental studies in space to measure the distribution of radiation dose inside cosmonauts’ bodies are conducted using so-called phantoms which simulate the composition of a human body. There are several generally accepted models of human body. These are an anthropomorphic phantom resembling a human torso, cylindrical and spherical phantoms. Russian science uses the spherical phantom. You can see it now. It is located in the Mini Research Module MRM1 behind starboard panel 205. 

On the spherical phantom you can see numerous pockets where dosimeters are inserted to measure surface radiation doses, that is, levels of radiation loads on human skin and crystalline lens.

Inside the spherical phantom there is a detector which measures the radiation dose at different distances from the surface.

There are active and passive detectors. Passive detectors measure the overall or, as they put it, the integral radiation, while the active ones can provide the time distribution of a dose. This particular experiment Matryoshka-R uses an active radiation meter Lyulin-5. The spherical phantom itself consists of different layers, which makes it possible to measure the dose received by human body at different depths. Periodically, we use this electronic unit to write the data from Lyulin-5 sensor to a special memory card, which we bring with us back to Earth. 

Having the information for the entire space mission, doctors can predict the effects of the radiation exposure on the crew and provide recommendations on whether the crew members can take part in subsequent space missions.

Narrated by Anatoly Ivanishin

Also used onboard the International Space Station is the Bubble Dosimeter equipment. The specialty of this equipment is that it allows to measure the contribution of neutrons to the radiation dose received by the crew. The equipment has the following sensors. As you can see, it is a flask filled with a special gel. It is in this flask that the bubbles are formed. 

Each of these bubbles represents a detected neutron. But in order to determine the dose of radiation received by the crew we do not need to count the number of bubbles. We use a special device. Let me show you now what it looks like. 

To determine the radiation level, we insert the detector into the Bubble Dosimeter control panel.

Select the Measurement mode. Enter the number of the detector. This device records all the necessary data, which includes: initialization time, duration of exposure, the number of bubbles, dose (dose rate), the file to which these data are written. 

After a measurement is taken, the detector needs to be deactivated to prevent bubbles from forming in it. This is done in the following manner. In such configuration the detector is put into storage until the next measurement session. 

And now I would like to come back to the discussion of personal means of monitoring the radiation doses received by the crew. We already spoke about personal dosimeters ID-3M, which the crew always carry on themselves. And now I want to show you one more device. It is a dosimeter, which is called Pille-ISS. Cosmonauts use during space walks. Prior to the space walk the dosimeter is reset to zero, and upon completion of the extravehicular activities it is possible to determine what radiation dose was received by the cosmonaut. Using the same method, it is possible to determine the radiation dose received by the cosmonauts during solar flares. In order to determine the radiation level we use the Pille control panel It is always fastened in its place behind Panel 125. And now I’m going to show it in more detail. 

You can now see the control panel of Pille-ISS. In order to take readings, the sensor is removed from its case and inserted in this socket. That’s how the sensor looks like. After that it is inserted into the socket. In this case the socket is occupied, because there is always a sensor in it operating in standby mode.

Thus you understand that radiation is and will be a serious hazard for a human being staying in space. For a space station in low-Earth orbit, numerous controls and various aids for protection against radiation have been developed. But for long-duration stay on the Moon and for missions to Mars, new and more advanced means of protecting human beings against radiation need to be developed.

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